Star Walk: Hold your phone toward the heavens and this $2.99 app will show you exactly which stars hang overhead. As you turn, the image spins with you, revealing constellations, planets, comets, and satellites in every direction. The team at Vito Technology has continuously improved this iPhone and iPad app. The current version lets you search for specific objects, double-tap to reveal detailed information, and turn back the clock to see the position of stars hours or centuries in the past.

Starmap: This $4.99 astronomy app digs deeper. Its "tonight" news feed points out the most notable features each day. You can narrow the selection to certain hours of the day; what celestial bodies interest you; or whether you'll be stargazing with binoculars, a telescope, or just the naked eye. Starmap works on iPhone and iPad.

Hubble Top 100: The European Southern Observatory has collected a gorgeous gallery of images taken by the Hubble Space Telescope. This iPad-only app takes full advantage of the tablet's bright, high-resolution screen. Colors and details really pop in this free app. While there's no clear Android counterpart, you can always check out spacetelescope.org for the ESO's full gallery.

Spot the Station: The International Space Station is the brightest object in the night sky after the moon. On a clear night, it glistens like a shooting star. Spot the Station will send you a text message when the ISS flies over your town, giving you a chance to catch it with your naked eye or make out some details with a pair of binoculars. Head to spotthestation.nasa.gov to sign up for the free service. Text message rates still apply.

[Editor's note: This is an updated version of an article that appeared in the July 29 issue of the Monitor weekly magazine.]